Review

There seems to be no limit to the amount of memory that can fit on a standard-size memory module. This, of course, is due to the memory chips that populate these boards—each new generation of memory chip fits more memory bits into approximately the same space. And not only is more memory squeezing into the essentially the same space, but performance is better, too, due to new memory schemes, such as double-data rate memory (DDR).

On the module front, a good example of this is the EBD11UD8ADFB and EBD11ED8ADFB 1 GB, non-buffered DIMMs from Elpida Memory (elpida.com). These modules use the company's EDD5108ADTA 512 Mb DDR400 SDRAMs, which were manufactured using a 0.11 µm process technology. They are organized as 64-million words by eight bits in TSOPs and operate at 200 MHz. Taking advantage of these DDR400 components, the two JEDEC-standard, 184-pin 1 GB PC3200 modules are organized as 128-million words by 64 and 72 bits by two ranks and feature 2.6V, ±0.1V operation. The DIMMs deliver data-transfer rates up to 3.2 GB/s.

Another type of the module, the PC2700-registered DDR DIMM from Smart Modular Technologies (smartm.com) is available in densities of 1, 2, 4, and 8 GB. The 1 GB DIMM features a data transfer rate of 2.7 GB/sec. The modules boost computing performance via a 333 MHz operating speed and, at 2" in height, are aimed at designs not constrained by height.

An interesting multichip module (MCM) memory device is the WEDPND16M72S- XBX 128-MB double data rate (DDR) SDRAM from White Electronic Designs (whiteedc. com). Housed in a 32 mm x 25 mm, 219-ball PBGA package, the device contains five DDR SDRAMs. This approach reduces board space requirements by 40%, offers a lower profile and reduces I/O connections by up to 19%, as well as reducing inductance and capacitance for low-noise performance. They are internally configured as a quad-bank DRAM with a synchronous interface.

Memory systems generally come in the form of disk drives, such as the the I35FB flash drive from Adtron (adtron.com), Capable of outpacing hard disk drives and of working in unfriendly environments, the drive sustains random access read/write rates of up to 30 MB/s. The drive relies on a media controller that adapts flash memory to the Ultra DMA-100 interface, a preferred standard in industrial automation and medical equipment applications. Via a standard IDE connector, the drive supports PIO Mode 0-4, multi-word DMA Mode 0-2, or UDMA-100 interfaces. Other features include ECC, wear-leveling, spare-sector mapping, 5V operation, and master or slave IDE configuration.

—Joe Desposito

Outlook

Modules Ply A Steady Course
Over the years, memory modules have played an integral role in the development of more powerful personal computers, servers and other computing equipment. And just as microprocessors have made enormous gains in operating speed and performance, so too have the memory modules that support them. So for 2004, we expect to see further gains in memory module speed and density. But as shown above, memory can be used in a variety of ways beyond the standard module. So we might expect some innovative memory products to appear in 2004.

—JD